Controlling TCP ACK transmission: Impact of discard ratio on performance in LTE-Advanced Pro

Recent research interest in cellular communication systems focuses on the design of the radio access networks (RAN) considering Transmission Control Protocol (TCP) behavior. However, less attention has been paid to the specific transmission method of TCP ACK. The authors have been studying methods including TCP ACK filtering that can well work with the link layer protocols in LTE-Advanced Pro (LTE-A Pro), where the TCP ACKs can be intentionally discarded. Basic methods of TCP ACK filtering have been investigated and it has been clarified that there is a method that can accomplish good TCP throughput with a reduced number of TCP ACKs. In this paper, we further study TCP ACK filtering and develop new methods, which are generalized methods of TCP ACK filtering. The novel feature of our new method is that the TCP ACK filtering can be controlled by a “discard ratio” parameter. The performance is evaluated by computer simulations. It is observed that the TCP throughput remains good even when the discard ratio is set to large values. In addition, it is found that there exists a value of the “discard ratio which can minimize the number of TCP ACKs while maintaining good TCP throughput.